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Monday, May 22, 2017

Graecopithecus Casts Doubt on "Out of Africa" Story of Human Origins

As reported in PLOS | One today, a 7.2 million year old fossil named Graecopithecus, from late Miocene Europe, suggests that the human line may have
originated in the Eastern Mediterranean (i.e. Europe), not Africa.

"In
this study, we propose based on root morphology a new possible
candidate for the hominin clade, Graecopithecus freybergi from Europe. "
[...]

"In contrast to the Ponginae, Graecopithecus shares derived
characters with African apes (ventrally shallow roots, buccolingually
broad molar roots; [32, 75]). Therefore, we consider four principle
alternative interpretations of its phylogenetic position:
Graecopithecus is a stem-hominine (last common ancestor of African apes
and Homo), a gorillin, a panin, or a hominin." [...]

"Accordingly, the
most parsimonious interpretation of the phylogenetic position of
Graecopithecus is that it is a hominin, although we acknowledge that the
known sample of fossil hominin root configurations is too small for
definitive conclusions."[...]

"Taken at face value, the derived
characters of Graecopithecus (p4 root morphology and possibly canine
root length) may indicate the presence of a hominin in the Balkans at
7.2 Ma." [...]

"Therefore, we submit that the dental root attributes of
Graecopithecus suggest hominin affinities, such that its hominin status
cannot be excluded. If this status is confirmed by additional fossil
evidence, Graecopithecus would be the oldest known hominin and the
oldest known crown hominine, as the evidence for the gorillin status of
Chororapithecus is much weaker than the hominin status of Graecopithecus
[8]. More fossils are needed but at this point it seems likely that the
Eastern Mediterranean needs to be considered as just as likely a place
of hominine diversification and hominin origins as tropical Africa."

"The phytolith record provides evidence of severe droughts, and the
charcoal analysis indicates recurring vegetation fires," said Böhme. "In
summary, we reconstruct a savannah, which fits with the giraffes,
gazelles, antelopes, and rhinoceroses that were found together with
Graecopithecus," Spassov added.

"The incipient formation of a desert
in North Africa more than seven million years ago and the spread of
savannahs in Southern Europe may have played a central role in the
splitting of the human and chimpanzee lineages," said Böhme. She calls
this hypothesis the North Side Story, recalling the thesis of Yves
Coppens, known as East Side Story.

"Transitional primate-like creatures
were evolving by
the end of the Mesozoic Era (ca. 65.5 million years ago)....The few placental mammals that
existed at that time mainly consisted of the insectivore ancestors of primates."

These
carnivorous ancestors of primates continued until about 55 million
years ago when some creatures resembling modern prosimians emerged. But
anthro.palomar.edu notes:

"Among the numerous Miocene primate species
were the ancestors of all modern apes and humans. By 14
million years ago, the group
of apes that included our ancestors was apparently in the process of adapting to
life on the edges of the expanding savannas in
Southern Europe."

[Graecopithecus was found in Southern Europe.]

The human line descends
from those primates that specialized in living on the savannas, not
those – like the ancestors of chimps – that specialized in the arboreal
habitats. On savannas, the predominant form of plant-life is grass,
while fruits are relatively scarce, especially during Ice Ages. Thus,
an animal can thrive on a savanna only if it eats grass, or animals that
eat grass. Humans are obviously not grass-eaters – we don't have the
multi-compartment guts adapted to fiber fermentation that is typical of
grass-eating animals. But an insectivore can find plenty of
grass-eating insects, such as grasshoppers, caterpillars, moth larvae,
grubs, crickets, and billbug larvae. It can also find small
grass-eating molluscs like snails.

The nutritional profile of insects is quite similar to wild game:

Insects are
wild game. Therefore an insectivore is already a predator adapted to eating wild
game. Insectivores have simple, carnivore-type guts. An insectivorous species would have to evolve new behaviors or gut features – hindgut
fermentation vats – to become predominantly frugivorous and deal with the fiber abundant in plants, as has
occurred in the great apes but not in humans. The great apes have
enormous guts adapted to fermenting fiber to convert it into saturated fats, mostly butyrate; healthy humans do not:

We have strong evidence that early Pleistocene humans – definite members of our genus – were ambush predators 2 million years ago.
We know that all definitely human ancestors – from Homo habilis 2
mya to present – were hunters and meat-eaters. Dunn could justify his
claim only by referring to the putative habits of ancient species who
were not human and are only suspected human ancestors (e.g.
Australpiths), while ignoring the heavy meat-eating habits of those
species that we know were human. Is that scientifically honest?

The truth is all known human
ancestors of modern humans, i.e. Homo habilis, Homo erectus,
Neanderthals, and Denisovans were predators, not vegetarians. Only
non-human species that might have been part of the human lineage,
such as Austalopiths, were largely plant-eaters. The hypothesis that human ancestors were nearly all vegetarians can't explain what we know about human evolution, and does
not align with what we know about the Earth's climate, flora and fauna
changes during the period of time when the human lineage evolved and
moved out of Africa.

While the savannas are expanding and forests shrinking during the
millions of predominantly Ice Age years, natural selection acts on an
insectivorous savanna species to favor those that prefer to eat fruits
and vegetables that don't exist on the savanna and are disappearing due
to the cold and dry climate, ultimately converting that insectivore with a simple carnivore-type gut into
a frugivorous, hindgut fermenter arboreal species; then natural selection changes course
completely, starts favoring the savanna-dwelling meat-eaters among those
fruit-eaters, progressively selects against the hindgut fermenters and eventually changes the members of this lineage back
into a savanna-dwelling apex predator species with a relatively simple, reduced volume carnivore-type gut with gastric acidity greater than most carnivores and comparable to scavenger species (the human line starting
at least 2 mya with Homo habilis).

While the savannas are expanding and forests shrinking (starting towards
the end of the Miocene, up to ~ 6 mya), natural selection favors the
reproduction of those members of an insectivorous savanna species who
capitalize on the increasing abundance of grass-eating insects, then
favors those who can capture and eat the even more energy-dense
grass-eating mammals (various rodents such as rabbits and gerbils), then
among those favors the individuals who are able to capture larger and
larger, more and more energy-dense, fat-rich game, ultimately
transforming the originally puny predatory primate (the insectivore)
into a mega-primate, the most predatory ape of all, the human, who hunted elephants for a living?

It seems to me that the second scenario is far more likely to be
what happened. In fact, due to the biological leaps and outright reversals (in dentition and intestinal form and function) required, I would
venture that the probability of the first scenario is near zero. If
chimps and humans have a common ancestor, that ancestor was
likely primarily an insectivore (chimps still are somewhat insectivorous). The chimp line
likely represents the descendants of that last common ancestor (LCA) who
chose to specialize in an arboreal habitat. The descendants of the LCA
who specialized in a savanna habitat retained their dominant predatory
way of life, and this line slowly graduated from insects and worms to
snakes, amphibians and other small animals, then to larger and larger
savanna animals until finally the highly carnivorous human emerged by 2 mya.

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